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- Title
<italic>In vitro</italic> antimicrobial activity of narasin against common clinical isolates associated with canine otitis externa.
- Authors
Chan, Wei Yee; Hickey, Elizabeth E.; Khazandi, Manouchehr; Page, Stephen W.; Trott, Darren J.; Hill, Peter B.
- Abstract
Background: Antimicrobial resistance and antimicrobial stewardship are of ever‐increasing importance in veterinary medicine. Re‐purposing of old drugs that are not used in human medicine is one approach that addresses the emergence of multidrug resistance in canine skin and ear infections, and can reduce the use of critically important human antibiotic classes. Hypothesis/Objectives: To determine the antimicrobial activity of narasin, a polyether ionophore conventionally used as a rumen modifier and anticoccidial agent in production animals, against common clinical isolates of canine otitis externa (OE). Animals/Isolates: Clinical isolates (<italic>n</italic> = 110) from canine OE were tested, including 17 meticillin‐susceptible <italic>Staphylococcus pseudintermedius</italic> (MSSP), 13 multidrug‐resistant <italic>Staphylococcus pseudintermedius</italic> (MDRSP), and 20 each of β‐haemolytic <italic>Streptococcus</italic> spp., <italic>Pseudomonas aeruginosa</italic>,<italic> Proteus mirabilis</italic> and <italic>Malassezia pachydermatis</italic>. Methods: Bacterial and yeast isolates were subcultured, suspended in broth and inoculated into 96‐well plates. Organisms were tested against concentrations of narasin ranging from 0.03 to 128 μg/mL. Minimal inhibitory concentrations (MICs) were determined after overnight incubation. Results: Narasin MICs for staphylococcal and streptococcal isolates ranged from 0.06 to 0.25 μg/mL; MIC50 and MIC90 values for both organisms were 0.125 μg/mL. No MICs were achieved for <italic>Pseudomonas</italic> or <italic>Proteus</italic> isolates. There was a weak antifungal effect against <italic>M. pachydermatis</italic> isolates (MIC 32 to >128 μg/mL). Conclusions and Clinical Relevance: Narasin was effective against Gram‐positive bacteria and had antifungal activity at higher concentrations against <italic>M. pachydermatis</italic>. However, the lack of Gram‐negative activity would prevent its use as a sole antimicrobial agent in cases of canine OE.
- Subjects
MULTIDRUG resistance in bacteria; OTITIS externa; ANTIBACTERIAL agents; DRUG efficacy; DOG diseases; VETERINARY epidemiology
- Publication
Veterinary Dermatology, 2018, Vol 29, Issue 2, p149
- ISSN
0959-4493
- Publication type
Article
- DOI
10.1111/vde.12516